These winds tend to keep the bitter cold air locked in the Arctic regions of the Northern Hemisphere. It is not a single storm. On occasion, this vortex can become distorted and dip much farther south than you would normally find it, allowing cold air to spill southward.

A person struggles to cross a street in blowing and falling snow as the Gateway Arch appears in the distance on Sunday, Jan. 5, 2014, in St. Louis, Missouri. (AP Photo/Jeff Roberson)

The polar vortex can lead to major cold air outbreaks in any portion of the Northern Hemisphere — North America, Europe and Asia.

A similar weather phenomenon in 2009 drove temperatures in the Midwest down to 22-below zero.

So why has it traveled so far south?

According to Frank Giannasca, senior meteorologist with The Weather, warmer air builds up over areas such as Greenland or Alaska, and that air forces the colder, denser air southward. Also, weather patterns can create the right conditions for the polar vortex to point south. But in this case, “this very well just may be one of those anomalies where it forces itself southward,” Giannasca said.

The good news? The frigid weather isn’t here to stay. Temperatures are expected to return to normal by the weekend.